Method of manipulating a pump

ABSTRACT

A method for removing a stator tube from a position about a rotor of a progressing cavity pump is provided. The apparatus includes an actuator assembly having a base and a piston which is longitudinally displaceable relative to the base, and a pusher rod. The base of the actuator assembly is removably attachable to a discharge end of the stator tube. The pusher rod is longitudinally releasably attachable to the piston at a plurality of locations along the length of the pusher rod and is located to engage the rotor when the base is coupled to the stator tube. The pusher rod is coupled to the piston and the piston is driven by the actuator assembly. With only slight modifications the apparatus may also be used to install the stator tube on the rotor when operated in a substantially opposite way.

TECHNICAL FIELD

The present disclosure relates generally to progressing cavity pumps,and more particularly, to a device for removing and/or installing thestator tube of a progressing cavity pump.

BACKGROUND

A conventional progressing cavity pump system, which can be used to pumpa wide range of fluids, typically includes an inlet chamber or suctionchamber, and a generally cylindrical stator tube having a dischargeport. The pump may include a rotor and a stator located inside thestator tube and having an internal bore extending longitudinallytherethrough. The rotor may be rotationally disposed in the internalbore of the stator tube. The stator may be in the form of a double leadhelical nut, in which case the stator may include a pair of internalhelical grooves which define the internal bore. Likewise, the rotor maybe a single lead helical screw rotor including one external helicallobe. The rotor may be rotationally disposed within the internal bore sothat the external helical lobe of the rotor and the internal helicalgrooves of the stator define a plurality of cavities therebetween. Thestator is typically formed from a resilient and flexible elastomericmaterial, and the rotor is typically manufactured from a metallicmaterial. The rotor may be rotatably driven by a drive shaft which maybe coupled to the rotor by a universal joint as is well known to thoseskilled in the cavity pump art. For additional information regarding theoperation and construction of progressing cavity pumps, reference can bemade to U.S. Pat. No. 2,512,764, U.S. Pat. No. 2,612,845, and U.S. Pat.No. 6,120,267.

As the rotor is rotatably driven within the stator bore, the cavitiesformed between the rotor and the stator progress from the suction end ofthe stator tube to the discharge end of the stator tube. In onerevolution of the rotor, two separate sets of cavities are formed, withone set of cavities being formed or opening at exactly the same rate asthe second set of cavities are closing. This pumping process results ina predictable, pulsationless flow of the fluid.

Because the stator is typically made from an elastomeric material, thestator may experience wear after a period of use. Therefore, it may bedesirable to remove the stator tube and stator from the progressingcavity pump system for reconditioning or replacement. Accordingly, thereis a need for a device for assisting in the removal and installation ofa stator tube of a progressing cavity pump.

SUMMARY

In one embodiment, the invention is an apparatus for removing a statortube from a position about a rotor of a progressing cavity pump, therotor being rotatable relative to the stator tube to pump materialthrough the stator tube. The apparatus includes an actuator assemblyhaving a base and a piston which is displaceable relative to the basealong a first axis, and a pusher rod. The base of the actuator assemblyis removably attachable to a discharge end of the stator tube. Thepusher rod is releasably attachable to the piston along the first axisat a plurality of locations along the pusher rod and is located toengage the rotor when the base is coupled to the stator tube, the pusherrod is coupled to the piston and the piston is driven by the, actuatorassembly.

The apparatus generally operates by pulling the stator tube off of therotor while using the rotor as a fixed ground point which provides aresistive force. By adjusting the position of the pusher rod withrespect to the piston along the first axis, the actuator assembly has anadjustable working length to enable the stator tube to be removed fromthe rotor of the progressing cavity pump.

Other objects and advantages will be apparent from the followingdescription and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective partially exploded view of one embodimentof the stator tube removal/installation device of the present inventionshown in conjunction with a stator tube;

FIG. 2 is a side partial cross section view of a conventionalprogressing cavity pump;

FIG. 3 is a side view of one embodiment of the stator tuberemoval/installation device of the present invention mounted to theprogressing cavity pump of FIG. 2, wherein the base of the stator tuberemoval/installation device is attached to the discharge end of thestator tube and the working end of the pusher rod is positioned adjacentto the discharge end of the rotor;

FIG. 4 is a side view of the stator tube removal/installation device andprogressing cavity pump of FIG. 3, wherein the piston of the stator tuberemoval/installation device is in a retracted position and wherein thebase and stator tube are spaced away from the rotor;

FIG. 5 is a side view of the stator tube removal/installation device andprogressing cavity pump of FIG. 4, wherein the piston of the stator tuberemoval/installation device is in an extended position;

FIG. 6 is a side view of the stator tube removal/installation device andprogressing cavity pump of FIG. 5, wherein the piston of the stator tuberemoval/installation device is in a retracted position;

FIG. 7 is a front perspective partially exploded view of anotherembodiment of the stator tube removal/installation device of the presentinvention shown in conjunction with a stator tube;

FIG. 8 is a side view of the stator tube removal/installation device andstator tube of FIG. 7, wherein a working end of the tension member ofthe stator tube removal/installation device is attached to the dischargeend of the rotor and the base of the stator tube removal/installationdevice is attached to the discharge end of the stator tube;

FIG. 9 is a side view of the stator tube removal/installation device andstator tube of FIG. 8, wherein the piston of the stator tuberemoval/installation device is in an extended position and wherein thebase of the stator tube removal/installation device and stator tube arepushed at least partially on the rotor;

FIG. 10 is a side view of the stator tube removal/installation deviceand stator tube of FIG. 9, wherein the piston of the stator tuberemoval/installation device is in a retracted position;

FIG. 11 is a side view of the stator tube removal/installation deviceand stator tube of FIG. 10, wherein the tension member of the statortube removal/installation device is longitudinally repositioned withrespect to the piston;

FIG. 12 is a side view of the stator tube removal/installation deviceand stator tube of FIG. 11, wherein the piston of the stator tuberemoval/installation device is in an extended position and wherein thebase of the stator tube removal/installation device and stator tube arepushed at least partially on the rotor; and

FIG. 13 is a front perspective partially exploded view of the piston ofthe stator tube removal/installation device of FIG. 7 shown inconjunction with a clip.

DETAILED DESCRIPTION

As shown in FIGS. 1 and 2, a conventional progressing cavity pumpsystem, generally designated 10, may include an inlet chamber or suctionchamber 12 and a cylindrical stator tube 16 having a discharge port 14.The stator tube 16 includes a suction end 30 that is coupled to, and influid communication with the inlet chamber 12. The pump,10 may furtherinclude a rotor 18 and a stator 20 located inside the stator tube 16,the stator tube 16 having an internal bore 22 extending longitudinallytherethrough. The stator 20 may be in the form of a double lead helicalnut, in which case the stator 20 may include a pair of internal helicalgrooves 23 a, 23 b which define the internal bore 22. Likewise, therotor 18 may be a single lead helical screw rotor including one externalhelical lobe. The rotor 18 may be rotationally disposed within theinternal bore 22 so that the external helical lobe of the rotor 18 andthe internal helical grooves of the stator 23 a, 23 b define a pluralityof cavities 24 therebetween. The stator 20 is typically formed from aresilient and flexible elastomeric material, and the rotor 18 istypically manufactured from a metallic material. The rotor 18 may berotatably driven by a drive shaft (not shown) which may be coupled tothe rotor 18 by a universal joint 28 as is well known to those skilledin the cavity pump art.

As the rotor 18 is rotatably driven within the stator bore 22, thecavities 24 formed between the rotor 18 and the stator 20 progress fromthe suction end 30 of the stator tube 16 to the discharge end 32 of thestator tube 16. In one revolution of the rotor 18, two separate sets ofcavities are formed, with one set of cavities being formed or opening atexactly the same rate as the second set of cavities are closing. Thispumping procedure results in a predictable, pulsationless flow of thefluid.

Because the stator 20 is typically made from an elastomeric material,the stator 20 may experience wear after a period of use. Therefore, itmay be desirable to remove the stator tube 16 and stator 20 from theprogressing cavity pump system 10 for reconditioning or replacement.

FIG. 1 illustrates one embodiment of an apparatus 34 for removing orinstalling the stator tube 16. The stator tube removal/installationdevice 34 may include an actuator assembly 36 having a base 37 and apiston 38 which is longitudinally displaceable relative to the base 37along a first axis 62. The base 37 may include a cross bar 48 whichincludes a pair of opposed slots 50 which are shaped and located toreceive a fastener 47 therethrough to couple the base 37 to thedischarge end 32 of the stator tube 16. The fasteners 47 that are usedto couple the base 37 and cross bar 48 to the stator tube 16 may includespacers 46 located thereon for spacing the base 37 from the stator tube16 when the base 37 is coupled to the stator tube 16.

The piston 38 can be driven by the base 37 along the first axis 62between an extended position, shown in FIGS. 3 and 5, and a retractedposition, shown in FIGS. 4 and 6. When the actuator assembly 36 is inthe retracted position a distal end 39 of the piston 38 (which is theend of the piston 38 that is located farthest from the stator tube 16when the actuator assembly 36 is mounted to the stator tube 16) islocated adjacent to the base 37. When the actuator assembly 36 is in theextended position the distal end 39 of the piston 38 is spaced away fromthe base 37 along the first axis 62, preferably at the outer limit ofthe range of motion of the piston 38 along the first axis 62. Themovement of driving the piston 38 from an extended position to theretracted position or from the retracted position to an extendedposition is termed a stroke, and the distance that the piston 38 movesbetween the extended position and the retracted position, or vice versa,is termed a stroke length.

In the embodiment shown in FIG. 1, the actuator assembly 36 is ahydraulic cylinder assembly and the piston 38 is a hollow piston.However, various other actuators may be used to drive the piston 38,including but not limited to pneumatic, electrically-powered andnon-cylindrical drivers. Additionally, although the piston 38 is shownand described as tubular, the piston 38 need not be hollow or have acircular cross section.

The stator tube removal/installation device 34 shown in FIG. 1 includesa pusher rod 40 that is received in and is concentric with the piston38. The pusher rod 40 is releasably attachable to the piston 38 alongthe first axis 62 at a plurality of locations along the pusher rod 40.In the embodiment shown in FIG. 1, the pusher rod 40 has a length thatis at least greater than a length of the piston 38 and includes aplurality of keyholes 42 spaced apart along the axial length of thepusher rod 40 by a distance about equal to a stoke length of theactuator assembly 36. The piston 38 may also include a keyhole 43located near its distal end 39. Accordingly, the pusher rod 40 can bereleasably coupled to the piston 38 for movement along the first axis 62by aligning one of the keyholes 42 of the pusher rod 40 with the keyhole43 of the piston 38, and pushing a pin 17 through the aligned keyholes42,43.

As noted above, the pusher rod 40 need not possess a circular crosssection, and the pusher rod 40 need not be received in the piston 38.For example, the pusher rod 40 and the piston 38 may be positioned sideby side or located in other arrangements. Additionally, any of a varietyof methods or structures of coupling the piston 38 and pusher rod 40 maybe used without departing from the scope of the invention such asclamps, fasteners, friction, and various inter-engaging geometries.

In order to remove the stator tube 16 of the pump 10 from the rotor 18,the base 37 of the actuator assembly 36 is coupled to the discharge end32 of the stator tube 16 such that the base 37 is located between thedistal end 39 of the piston 38 and the stator tube 16. The actuatorassembly 36 should be coupled to the stator tube 16 to prevent theactuator assembly 36 from pushing itself away from the stator tube 16when the actuator assembly 36 is activated. In one embodiment, athreaded fastener 47 is passed through each of the slots 50 and throughan opening 53 of the discharge end 32 of the stator tube 16, and nuts 57are threaded onto each end of the fasteners 47. The spacers 46 on thefasteners 47 provide a gap between the stator tube 16 and the actuatorassembly 36 which may permit an operator to visually align the workingend 44 of the pusher rod 40 with the discharge end of the rotor 18 asthe base 37 is mounted to the stator tube 16. Next, the stator tube 16is disconnected from the progressing cavity pump system 10 (i.e.disconnected from the inlet chamber 12). The piston 38 is then moved toits extended position, and the pusher rod 40 is coupled to the piston 38such that the working end 44 of the pusher rod 40 is located andadjacent to the rotor 18, as shown in FIG. 3. Accordingly, as shown, thebase 37 of the actuator assembly 36 is located between the working end44 of the pusher rod 40 and the distal end 39 of the piston 38.

The actuator assembly 36 is then activated or stroked such that thepiston 38 and associated pusher rod 40 are moved in the direction ofarrow A toward the discharge end of the rotor 18. Because the rotor 18is either fixed along the first axis 62 or because the rotor 18 andassociated progressing cavity pump system 10 possess a great deal moremass than the stator tube 16 and base 37, when the working end 44 of thepusher rod 40 engages the discharge end of the rotor 18, the rotor 18will exert a resistive force on the working end 44 of the pusher rod 40.As a result of force exerted on the piston 38 by the actuator assembly36, the base 37 and associated stator tube 16 will be pulled in thedirection of arrow B toward the distal end 39 of the piston 38 and awayfrom the rotor 18. The step of activating or stroking the actuatorassembly 36 is then continued until the piston 38 is moved from itsextended position (FIG. 3) to its retracted position (FIG. 4). Duringthis time, the stator tube 16 is pushed at least partially off of therotor 18 by a distance approximately equal to a the stroke length of theactuator assembly 36. Due to the shape of the rotor 18 and stator tube16, the stator tube 16 and the stator tube removal/installation device34 may be rotated about the first axis 62 as the stator tube 16 ispulled off of the rotor 18.

In the embodiment shown in FIGS. 1-7, the stroke length of the actuatorassembly 36 is shorter than the length of the stator tube 16, in whichcase the stator tube 16 cannot be removed from its position about therotor 18 in a single stroke. Accordingly, the stator tuberemoval/installation device 34 must pull the stator tube 16 from itsposition about the rotor 18 in a series of repeated steps. To accomplishthe removal operation in a series of steps, the stator tuberemoval/installation device 34 is provided with a variable workinglength that can be adjusted along the first axis 62 between each strokeof the actuator assembly 36 as the stator tube 16 is incrementallyremoved. Specifically, a pin connection may be used to enable theposition of the pusher rod 40 to be adjusted with respect to the piston38 along the first axis 62 using the pin connection.

In particular, when the stroke length of the actuator assembly 36 isshorter than the length of the stator tube 16, the stator tuberemoval/installation device 34 must be adjusted and reactivated in orderto fully remove the stator tube 16 from the rotor 18. In this case, thenext step in the removal operation is to deactivate the actuatorassembly 36 such that the piston 38 reciprocates back from its retractedposition to its extended position. Likewise, the pusher rod 40, which iscoupled to the piston 38, is carried with the piston 38 and moved awayfrom the rotor 18 such that the working end 44 of the pusher rod 40 nolonger engages the discharge end of the rotor 18. Then, as shown in FIG.5, the pin 17 which couples the pusher rod 40 and the piston 38 isremoved and the working end 44 of the pusher rod 40 is movedlongitudinally along the first axis 62 such that the pusher rod 40 islocated adjacent to the rotor 18. The pin 17 is then passed through thealigned keyholes 42, 43 to couple the pusher rod 40 and piston 38together. In this manner the working length of the stator tuberemoval/installation device 34 can be adjusted to accommodate the newposition of the stator tube 16 relative to the rotor 18 after theprevious stoke of the actuator assembly 36.

Referring to FIG. 6, the next step is to reactivate the actuatorassembly 36 such that the piston 38 and pusher rod 40 move in thedirection of arrow C. Again, when the working end 44 of the pusher rod40 engages the discharge end of the rotor 18, the rotor 18 exerts aresistive force which causes the piston 38 to push the base 37 andstator tube 16 in the direction of arrow D toward the distal end 39 ofthe piston 38 and away from the rotor 18. The step of reactivating orstroking the actuator assembly 36 is continued until the piston 38 ismoved from its extended position to its retracted position. Accordingly,the stator tube 16 is again pushed off of the rotor 18 by a distanceapproximately equal to a the stroke length of the actuator assembly 36.

The steps of deactivating the actuator assembly 36, decoupling thepusher rod 40 and the piston 38, adjusting the longitudinal position ofthe pusher rod 40 with respect to the piston 38 along the first axis 62,coupling the pusher rod 40 and the piston 38, and reactivating theactuator assembly 36, are then repeated as necessary until the statortube 16 is completely removed from the rotor 18.

In addition to the previously described removal operation, the statortube removal/installation device 34 shown in FIG. 1 may be slightlymodified and used to install a stator tube 16 onto a rotor 18.Specifically, in order to install the stator tube 16 onto a rotor 18 ofa progressing cavity pump system 10 using the stator tuberemoval/installation device 34, an I-bolt or other attachment mechanismmay be installed on the rotor 18 so that a tension member 52 can beattached to the rotor 18. As shown in FIG. 7, the tension member 52 maytake the place of the pusher rod 40 when the stator tuberemoval/installation device 34 is used in an installation operation. Inthe embodiment shown in FIG. 7 the tension member 52 is a chain.However, the tension member 52 may be nearly any structure that cancarry a tension load, such as a rod nearly identical to the pusher rod40. Nevertheless, a chain may be preferred because each link of thechain provides an opening that can receive a pin therethrough.Furthermore, the tension member 52 is preferably generally flexible atleast at its end that is coupled to the rotor 18 to accommodate anymovement of the rotor 18 relative to the stator tube 16. If the tensionmember 18 is not flexible itself, the tension member may otherwiseflexibly coupled to the rotor 18. Accordingly, if a rod is used as thetension member, the tension member may include a short length of chain,a universal joint, etc., to provide a flexible connection to the rotor18. In addition, various other methods and structure for attaching thetension member 52 to the rotor 18 may be used, such as passing thetension member 52 through a hole in the rotor 18, passing the tensionmember 52 about the rotor 18, etc.

In order to install the stator tube 16 on the rotor 18, a working end 54of the tension member 52 is attached to the rotor 18, preferably at thedischarge end 60 (See FIG. 8). The tension member 52 is also passedthrough the stator tube 16, the actuator assembly 36 and the piston 38.Next the base 37 of the actuator assembly 36 is attached to thedischarge end 32 of the stator tube 16 and the suction end 30 of thestator tube 16 is positioned adjacent to the discharge end 60 of therotor 18. The base 37 is coupled to the stator tube 16 to enable theactuator assembly 36 to remain properly aligned with the rotor 18 duringthe installation process. The tension member 52 is then coupled to thepiston 38 for movement along the first axis 62 by passing the pin 17through the keyhole 43 and a link in the tension member 52. Of coursevarious other methods or structures for coupling the piston 38 and thetension member 52 may be used. For example, referring to FIG. 13, a clip64 having an outside dimension that is larger than an outside dimensionof the piston 38 and having a slot 66 for receiving a link of thetension member 52 may be slid over a link of the tension member 52adjacent to the distal end 39 of the piston 38 to prevent movement ofthe tension member 52 relative to the piston 38 toward the rotor 18along the first axis 62. The tension member 52 is preferably coupled tothe piston 38 such that no more than a small amount of slack exists inthe tension member 52 between the attachment to the discharge end of therotor 18 and the connection to the piston 38.

Referring to FIG. 9, the next step is to activate or stroke the actuatorassembly 36 such that the piston 38 and tension member 52 are moved inthe direction of arrow E away from the discharge end of the rotor 18.Because the rotor 18 is either fixed along the first axis 62 or becausethe rotor 18 and associated progressing cavity pump system 10 possess agreat deal more mass than the stator tube 16 and the base 37, when thetension member 52 is pulled tight between the pin connection to thepiston 38 and the discharge end 60 of the rotor 18, the rotor 18 exertsa resistive force. As a result of force exerted on the piston 38 by theactuator assembly 36, the base 37 and stator tube 16 will be pushed inthe direction of arrow F away from the distal end 39 of the piston 38and toward the rotor 18. The step of activating or stroking the actuatorassembly 36 is then continued until the piston 38 is moved from itsretracted position to its extended position. Accordingly, the statortube 16 is slid on to the rotor 18 for a distance approximately equal toa the stroke length of the actuator assembly 36. The stator tube 16 maybe rotated as it slides onto the rotor 18.

Thus, when performing an installation operation, the stator tuberemoval/installation device 34 pushes the stator tube 16 to a positionabout the rotor 18 using the rotor 18 as an anchor point. In general,after the tension member 52 is attached to the discharge end 60 of therotor 18 and the base 37 of the actuator assembly 36 is mounted to thedischarge end 32 of the stator tube 16, the tension member 52, which iscoupled to the piston 38 via pin 17, is put in tension by driving thepiston 38 away from the rotor 18. Then, as a result of force exerted onthe piston 38 by the actuator assembly 36 during its stroke, the base 37and stator tube 16 are forced away from distal end 39 of the piston 38and toward the rotor 18.

Because the stroke length of the actuator assembly 36 may be shorterthan the length of the stator tube 16, the stator tuberemoval/installation device 34 may be required to be adjusted andreactivated in order to fully install the stator tube 16 about the rotor18. In this case the next step in the installation operation is todeactivate the actuator assembly 36 such that the piston 38 reciprocatesback from its extended position to its retracted position (see FIG. 10).Likewise, the distal end of the tension member 52, which is coupled tothe piston 38, is moved toward the rotor 18 such that the tension member52 is slack. Then, as shown in FIG. 11, the pin 17 coupling the tensionmember 52 and the piston 38 is removed and the tension member 52 ispulled through the piston 38 to remove any slack in the tension member52. The pin 17 is then repositioned to couple the tension member 52 andthe piston 38 together. In this manner the working length of the statortube removal/installation device 34 can be adjusted to accommodate thenew position of the stator tube 16 relative to the rotor 18 after theprevious stoke of the actuator assembly 36.

Referring to FIG. 12, the next step is to reactivate the actuatorassembly 36 such that the piston 38 and pusher rod 40 move in thedirection of arrow G. Again, when the tension member 52 is pulled tightbetween the discharge end of the rotor 18 and the pin connection to thepiston 38, the rotor 18 will exert a resistive force. As a result offorce exerted on the piston 38 by the actuator assembly 36, the base 37and associated stator tube 16 will be pushed in the direction of arrow Haway from the distal end 39 of the piston 38 and toward the rotor 18.The step of reactivating or stroking the actuator assembly 36 iscontinued until the piston 38 is moved from its retracted position toits extended position. Accordingly, the stator tube 16 is slid over therotor 18 for a distance approximately equal to a the stroke length ofthe actuator assembly 36.

The steps of deactivating the actuator assembly 36, decoupling thetension member 52 and the piston 38, adjusting the longitudinal positionof the tension member 52 with respect to the piston 38 along the firstaxis 62, coupling the tension member 52 and the piston 38, andreactivating the actuator assembly 36, can be repeated as necessaryuntil the stator tube 16 is installed in the desired position about therotor 18. The stator tube 16 can then be coupled to the suction chamber12, and the tension member 52 can be uncoupled from the rotor 18.Finally, the stator tube removal/installation device 34 can be uncoupledfrom the stator tube 16.

Having described the invention in detail and by reference to thepreferred embodiment, it will be apparent that modifications andvariations thereof are possible without departing from the scope of theinvention.

What is claimed is:
 1. A method for manipulating a pump, the pumpincluding a rotor received inside a stator tube, the rotor beingrotatable relative to said stator tube to pump material through saidstator tube, the method comprising the steps of: providing an apparatusincluding an actuator assembly having a base and a piston that isdisplaceable relative to said base along a first axis and a pusher rodlocated adjacent to said piston; attaching said base to a discharge endof said stator tube; coupling said pusher rod to said piston formovement along said first axis; and activating said actuator assemblysuch that said piston and pusher rod are displaced relative to said basealong said first axis such that a working-end of said pusher rod engagessaid rotor which provides a resistive force as said base and stator tubeare spaced away from said rotor along said first axis by said actuatorassembly.
 2. The method of claim 1, wherein said piston is in anextended position during said coupling step and wherein said activatingstep is continued until said piston is in a retracted position, andwherein the method further includes the steps of uncoupling said pusherrod from said piston, deactivating said actuator assembly to move saidpiston to said extended position, and coupling said pusher rod to saidpiston for movement along said first axis.
 3. The method of claim 2further comprising the step of reactivating said actuator assembly todisplace said piston and pusher rod along said first axis such that saidworking end of said pusher rod engages said rotor and said base andstator tube are spaced away from said rotor along said first axis bysaid actuator assembly.
 4. The method of claim 3, wherein saiduncoupling, deactivating, coupling and reactivating steps are repeateduntil said stator tube is removed from said rotor.
 5. The method ofclaim 1, wherein said pusher rod includes a plurality of keyholes spacedalong a length thereof and said piston includes at least one keyhole,and wherein said coupling step includes aligning one of said keyholes ofsaid pusher rod with said keyhole of said piston and passing a pinthrough said aligned keyholes.
 6. The method of claim 1, wherein saidpump is a progressing cavity pump, said rotor is a single lead helicalscrew rotor, said stator tube includes a double lead helical cavitytherein, and said stator tube is rotated about said first axis relativeto said rotor during said activating step.
 7. The method of claim 1,further comprising the steps of: providing a flexible tension membercoupling said tension member to said rotor for movement along said firstaxis; coupling said tension member to said piston for movement alongsaid first axis; and activating said actuator assembly such that saidstator tube is moved towards said rotor to urge said stator tube ontosaid rotor.
 8. The method of claim 7, further comprising the steps of:moving said piston from an extended position to a retracted position;uncoupling said tension member and said piston from a first position;coupling said tension member to said piston at a second position formovement along said first axis; activating said piston such that saidstator tube is moved towards said rotor to urge said stator tube ontosaid rotor; and repeating said uncoupling, moving, coupling, andactivating steps until said stator tube is mounted on said rotor.
 9. Amethod for installing a stator tube on a rotor of a pump comprising thesteps of: providing an apparatus including an actuator assembly having abase, a piston that is displaceable relative to said base along a firstaxis, and a tension member; attaching a working end of said tensionmember to said rotor; attaching said base to a discharge end of saidstator tube; coupling said tension member to said piston for movementalong said first axis; and activating said actuator assembly such thatsaid piston and tension member are displaced relative to said base alongsaid first axis such that the working end of the tension member pulls onsaid rotor which provides a resistive force as said base and said statortube are moved along said first axis toward said rotor to urge saidstator tube onto said rotor.
 10. The method of claim 9 wherein saidpiston is in a retracted position during said coupling step and whereinsaid activating step is continued until said piston is in an extendedposition.
 11. The method of claim 10, further comprising the steps of:deactivating said actuator assembly to move said piston to saidretracted position; uncoupling said tension member and said piston froma first position; coupling said tension member and said piston at asecond position; reactivating said actuator assembly such that saidpiston and tension member are displaced relative to said base along saidfirst axis such that the working end of the tension member pulls on saidrotor which provides a resistive force as said base and said stator tubeare moved along said first axis toward said rotor to urge said statortube onto said rotor; and repeating said deactivating, uncoupling,coupling, and reactivating steps until said stator tube is mounted onsaid rotor.